3 ms·

Interactive Programming in C (2014)

91 points by ofalkaed 1y ago

lkuty 1y ago
Tsoding made a video about hot code reloading in C (https://www.youtube.com/watch?v=Y57ruDOwH1g https://www.youtube.com/watch?v=Y57ruDOwH1g) and also used the same concept in "My Own 3b1b Animation Engine but in C" (https://www.youtube.com/watch?v=RVwuYgXNUCM https://www.youtube.com/watch?v=RVwuYgXNUCM).
uticus 1y ago
> When the library loads without error, look up the GAME_API struct.... If looking up the GAME_API fails, close the handle and consider it a failure. Error handling strategies, and what fallback state things fall into when the hot code breaks, would be great to hear about.
90s_dev 1y ago
I did something similar ones as a vs code extension for love2d which I called live2d, so that you could develop your game while it was running. It was incredibly fun, but incredibly hard to use, and nobody had any interest in it, so I abandoned it and lost the source code eventually. But it worked so well. I had invented this thing called magic tables to go along with it and make it easier to use, I forgot what they did, I just remember the name and how cool it was.
- fao_ 1y ago
  My favourite go-to for that in Love2D has been rxi's lurker: https://github.com/rxi/lurker https://github.com/rxi/lurker
  - binary132 1y ago
    How well does this work?
RustyRussell 1y ago
Andrew Tridgell's KnightCap did this differently: it's a network chess server, and it would dump its data to a file and re-exec. The trick here is that it would keep the (network) fds open for zero downtime. IIRC he used a Perl script called datadumper to gen the code marshal/demarshal the structures. This has the advantage that reboots can be handled fairly seemlessly too (though there will be reconnections then of).
- sitkack 1y ago
  https://man7.org/linux/man-pages/man2/pidfd_getfd.2.html https://man7.org/linux/man-pages/man2/pidfd_getfd.2.html https://gist.github.com/kentonv/bc7592af98c68ba2738f4436920868dc https://gist.github.com/kentonv/bc7592af98c68ba2738f44369208... For those curious research "SCM_RIGHTS" (Socket-Level Control Message) and sendmsg/recvmsg
- o11c 1y ago
  The main disadvantage of this is that most encryption libraries don't support serializing their state.
  - fao_ 1y ago
    Eh, you could probably get away with it if you use BearSSL[0]. The only difficulty would be: These elements can be allocated anywhere in (writable) memory, e.g. heap, data segment or stack. They must not be moved while in use (they may contain pointers to each other and to themselves). Which you could probably get around with by just keeping track of offsets and using mmap [0]: https://www.bearssl.org/api1.html https://www.bearssl.org/api1.html
zoom6628 1y ago
Maybe TinyC from Ballard et al could also be used given its ability to be a C interpreter?
mrheosuper 1y ago
iirc HolyC is an interpret language.
saagarjha 1y ago
I use the debugger a lot for REPL-like workflows.

91 points by ofalkaed 1y ago

Tsoding made a video about hot code reloading in C (https://www.youtube.com/watch?v=Y57ruDOwH1g https://www.youtube.com/watch?v=Y57ruDOwH1g) and also used the same concept in "My Own 3b1b Animation Engine but in C" (https://www.youtube.com/watch?v=RVwuYgXNUCM https://www.youtube.com/watch?v=RVwuYgXNUCM).

uticus 1y ago

> When the library loads without error, look up the GAME_API struct.... If looking up the GAME_API fails, close the handle and consider it a failure. Error handling strategies, and what fallback state things fall into when the hot code breaks, would be great to hear about.

90s_dev 1y ago

I did something similar ones as a vs code extension for love2d which I called live2d, so that you could develop your game while it was running. It was incredibly fun, but incredibly hard to use, and nobody had any interest in it, so I abandoned it and lost the source code eventually. But it worked so well. I had invented this thing called magic tables to go along with it and make it easier to use, I forgot what they did, I just remember the name and how cool it was.

fao_ 1y ago
My favourite go-to for that in Love2D has been rxi's lurker: https://github.com/rxi/lurker https://github.com/rxi/lurker
- binary132 1y ago
  How well does this work?

RustyRussell 1y ago

Andrew Tridgell's KnightCap did this differently: it's a network chess server, and it would dump its data to a file and re-exec. The trick here is that it would keep the (network) fds open for zero downtime. IIRC he used a Perl script called datadumper to gen the code marshal/demarshal the structures. This has the advantage that reboots can be handled fairly seemlessly too (though there will be reconnections then of).

sitkack 1y ago
https://man7.org/linux/man-pages/man2/pidfd_getfd.2.html https://man7.org/linux/man-pages/man2/pidfd_getfd.2.html https://gist.github.com/kentonv/bc7592af98c68ba2738f4436920868dc https://gist.github.com/kentonv/bc7592af98c68ba2738f44369208... For those curious research "SCM_RIGHTS" (Socket-Level Control Message) and sendmsg/recvmsg
o11c 1y ago
The main disadvantage of this is that most encryption libraries don't support serializing their state.
- fao_ 1y ago
  Eh, you could probably get away with it if you use BearSSL[0]. The only difficulty would be: These elements can be allocated anywhere in (writable) memory, e.g. heap, data segment or stack. They must not be moved while in use (they may contain pointers to each other and to themselves). Which you could probably get around with by just keeping track of offsets and using mmap [0]: https://www.bearssl.org/api1.html https://www.bearssl.org/api1.html

zoom6628 1y ago

Maybe TinyC from Ballard et al could also be used given its ability to be a C interpreter?

mrheosuper 1y ago

iirc HolyC is an interpret language.

saagarjha 1y ago

I use the debugger a lot for REPL-like workflows.